Fabrication of silicon microclusters and microfilaments

Abstract

An ablation process by which fused deposits of silicon particles are accuated on a substrate of selected material in accordance with whether microclusters of spherical configurations or microfilaments of cylindrical configurations are to be fabricated. Silicon ablation is accomplished in an inert gas atmosphere with an excimer laser that generates light pulses of which the wavelength and frequency are controlled to fix the energy level thereof. The pressure of the inert gas atmosphere is also controlled in accordance with whether microclusters or microfilaments are to be fabricated.

What we claim is: 
     
       1. An ablation process for fabricating porous silicon microclusters comprising: using laser light pulses in an inert atmosphere of argon gas pressurized in a range of 20-200 mTorr to derive a plasma of particles which have a surface chemistry and extend along a path from a block of silicon material, with the laser light pulses having a wavelength of 248 nanometers, a frequency ranging from 25 to 35 Hz and a laser fluence of 150 mJ/mm 2  ;   locating a substrate having a gold film on a quartz base, in the path of the particles; and   accumulating fused deposits of the particles on the substrate, with the particles having spherical configurations ranging in diameter from 200 to 1000 Angstrom units.   
     
     
       2. The process of claim 1 wherein at least one dopant is incorporated with the silicon block to control the surface chemistry of the fused deposits. 
     
     
       3. The process of claim 1 wherein at least one chemically active gas is included with the argon gas to control the surface chemistry of the fused deposits. 
     
     
       4. The process of claim 1 wherein the argon gas is pressurized at 150 mTorr, while the frequency of the light pulses is 30 Hz and the fused deposits of spherical configurations are accumulated in a deposition time of 12 minutes. 
     
     
       5. An ablation process for fabricating porous silicon microfilaments, comprising: using laser light pulses in an inert atmosphere of argon gas pressurized in a range of 0.05-0.5 Atmospheres to derive a plasma of particles which have a surface chemistry and extend along a path from a block of silicon material, with the laser light pulses having a wavelength of 248 nanometers, a frequency ranging from 5 to 15 Hz and a laser fluence of 150 mJ/mm 2  ;   locating a substrate of oscillator-quality quartz in the path of the particles; and   accumulating fused deposits of cylindrical configurations ranging in diameter from 1000 Angstrom units to 1 micron and in length up to several microns.   
     
     
       6. The process of claim 5 wherein the argon gas is pressurized at 0.2 Atmospheres, while the frequency of the light pulses is 10 Hz and the fused deposits of cylindrical configurations are accumulated in a deposition time of 12 minutes. 
     
     
       7. The process of claim 5 wherein at least one dopant is incorporated with the silicon block to control the surface chemistry of the fused deposits. 
     
     
       8. The process of claim 5 wherein at least one chemically active gas is included with the argon gas to control the surface chemistry of the fused deposits. 
     
     
       9. The process of claim 6 wherein at least one dopant is incorporated with the silicon block to control the surface chemistry of the fused deposits. 
     
     
       10. The process of claim 6 wherein at least one chemically active gas is included with the argon gas to control the surface chemistry of the fused deposits.